Tag Archives: Egypt

Time for an update on the Somabay Egyptian Solar Challenge. Scrutineering was due to have begun, but apparently all the cars are still held up in customs. Hopefully the race itself will still start on the 17th. Apparently the route will run north and south along the Red Sea shore for four days, and finish at the Pyramids of Giza on the fifth day.

With luck, we will get some news from mostdece during the race, because the official Twitter and Facebook feeds are not saying much. The following three teams have active news feeds:

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The solar car teams below have said that they intend to race at the Somabay Egyptian Solar Challenge this March. Details of the race are still rather thin on the ground – no route has yet been announced, and there is no official list of teams. There are, however, Twitter and Facebook feeds for the race. Those thinking about participating should probably note the travel advice from Australian, US, Dutch, and French authorities.

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In 1949, Willard Libby proposed carbon dating, a method for dating carbon-containing objects (like wood, leather, or cloth) that exploits the radioactive decay of carbon-14. The diagram above [redrawn from J. R. Arnold & W. F. Libby, “Age Determinations by Radiocarbon Content: Checks with Samples of Known Age,” Science110 (2869), 678–680, 23 Dec 1949] shows the decay curve for carbon-14, together with some comparison samples Libby used (including wood dated by tree rings and items from the tomb of Pharaoh Zoser, for whom the first of the pyramids was built). It’s a very good fit! Later tests of carbon-dating have used dendrochronology back to about 10,000 BC.

The carbon in plants contains about one part per trillion of carbon-14, which the plants absorb from the atmosphere. The same amount of carbon-14 is present in animals, which get their carbon by eating plants or other animals. All living things therefore contain about one part per trillion of carbon-14. In dead plants or animals, however, the carbon-14 decays with a half-life of 5,730 years. For practical dating purposes, measurements of carbon-14 are adjusted to match the tree-ring data, so as to compensate for small changes in the amount of atmospheric carbon-14 over time. Such calibrated dates are reported as “Before Present” (BP), where “Present” means 1 January 1950.

One of the most famous examples of carbon-dating has been the Shroud of Turin, purported to be the burial shroud of Jesus Christ, and shown below in a negative image from 1898. The Shroud has been carbon-dated to between 1260 and 1390 AD, which is consistent with its denunciation as a forgery by the Bishop of Troyes in 1389, shortly after it first appeared on the historical scene. For the dating story, see P. E. Damon et al., “Radiocarbon Dating of the Shroud of Turin,” Nature337 (6208), 611–615, 16 Feb 1989.